NICS

In NMR experiments one can only measure the CSs in a limited set of points in space (the nuclei positions r ). However, the induced field and, consequently, the nuclear shielding tensor, are defined and can be computed for aU points in space such that one can drop the index i from Equation 12.4 and calculate the shielding tensor at any arbitrary position r, yielding the so-called nucleus-independent chemical shifts (NICS) [24]. NICS values are, thus, not referenced with respect to any nucleus and that is why they are nucleus independent. Also, and similarly to site-specific shieldings, rather than dealing with the shielding itself, one frequently reports the isotropic NICS shift (5j, j,5) defined as follows  

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D. Marx and J. Hiitter, in Modern Methods and Algorithms of Quantum Chemistry, J. GrotendorsC, ed., John von Neumann Institute for Computing, Julich, Germany, 2000, pp. 301-449. See http //www.fz-juelich,de/nic-series. 

This determines the total flux at the li/nic of viscous flow. Equations (5.18 and (5.19) therefore describe the limiting form of the dusty gas model for high pressure or large pore diameters -- the limit of bulk diffusion control and viscous flow,... 

Molecula.rMecha.nics. Molecular mechanics (MM), or empirical force field methods (EFF), ate so called because they are a model based on equations from Newtonian mechanics. This model assumes that atoms are hard spheres attached by networks of springs, with discrete force constants. 

Several international organizations have been estabUshed that can offer conservation advice or even practical help in areas of the world where such is not readily available. The International Centre for the Study of the Preservation and the Conservation of Cultural Properties (ICCROM), based in Rome, is an intergovernmental organization that serves over 80 member states, among which is the United States. In the United States, the National Institute for Conservation of Cultural Property (NIC) serves as a fomm to faciUtate information distribution and exchange, coordination and planning between institutions and representatives of the various professions, and to promote pubHc and government awareness of the need for conservation of the cultural... 

Orga.nic Carbon. Organic materials interfere with plant operation because these compounds react with sulfuric acid under furnace conditions to form sulfur dioxide. There is a reducing atmosphere in the furnace which may reduce sulfur dioxide to elemental sulfur, which results in sulfur deposits in the gas handling system. 

Mech nic lProperties. Extensive Hsts of the physical properties of FEP copolymers are given in References 58—63. Mechanical properties are shown in Table 3. Most of the important properties of FEP are similar to those of PTFE the main difference is the lower continuous service temperature of 204°C of FEP compared to that of 260°C of PTFE. The flexibiUty at low temperatures and the low coefficients of friction and stabiUty at high temperatures are relatively independent of fabrication conditions. Unlike PTFE, FEP resins do not exhibit a marked change in volume at room temperature, because they do not have a first-order transition at 19°C. They ate usehil above —267°C and are highly flexible above —79°C (64). 

Bot nic l nd Animal Extracts. Tinctures and fluid and soHd extracts of items such as vanilla, coffee, cocoa, and Hcorice are produced by treating the raw materials with a solvent. Vanilla is by far the most widely used extract and is often found in chocolate products, baked goods, beverages, and frozen desserts (49,52). 

G lv nic Corrosion. Galvanic corrosion is an electrochemical process with four fundamental requirements (/) an anode (magnesium), 2) a cathode (steel, brass, or graphite component), (J) direct anode to cathode electrical contact, and (4) an electrolyte bridge at the anode and cathode interface, eg, salt water bridging the adjacent surfaces of steel and magnesium components. If any one of these is lacking, the process does not occur (133,134). 

Mech nic lF tig ue. Some mechanical fatigue tests have been conducted on explosion-clad composites where the plane of maximum tensile stress is placed near the bond 2one (30). 

Three tachykinin GPCRs, NK, NK, and NK, have been identified and cloned. AH are coupled to phosphatidjhnositol hydrolysis. The NK receptor is selective for substance P (SP) and is relatively abundant in the brain, spinal cord, and peripheral tissues. The NK receptor is selective for NKA and is present in the gastrointestinal tract, urinary bladder, and adrenal gland but is low or absent in the CNS. The NIC receptor is selective for NKB and is present in low amounts in the gastrointestinal tract and urinary bladder, but is abundant in some areas of the CNS, ie, the spinal dorsal bom, soUtary nucleus, and laminae IV and V of the cortex with moderate amounts in the interpeduncular nucleus. Mismatches in the distribution of the tachykinins and tachykinin receptors suggest the possibility of additional tachykinin receptor subtypes. 

Mech nic l Impact Mills. The mechanical types include cmshers, hammer mills, pin disk mills, turbine mills, and mills with air classifiers. Impact Crusher. Feed material is introduced through a feed opening onto a rotor moving at between 25 and 50 m/s (Fig. 11). The initial impact by the rotor causes some size reduction, and the material is accelerated up to the speed of the rotor and flung against the impact plates, where further size reduction occurs. It is possible to wear-protect these units quite well, so that abrasive materials can be handled. The final end particle size can be varied by the inclusion of an outlet grid to vary the residence time in the machine. 

Orga.nic Chemistry. The organic chemistry of sulfur dioxide, particularly as it relates to food appHcations, has been discussed (246). Although no reaction takes place with saturated hydrocarbons at moderate temperatures, the simultaneous passage of sulfur dioxide and oxygen into an alkane in the presence of a free-radical initiator or ultraviolet light affords a sulfonic acid such as hexanesulfonic acid [13595-73-8]. This is the so-called sulfoxidation reaction (247) ... 

Orga.nic Colora.nts. The importance of coal-tar colorants cannot be overemphasized. The cosmetic industry, in cooperation with the FDA, has spent a great deal of time and money in efforts to estabUsh the safety of these dyes (see Colorants for food, drugs, cosmetics, and medical devices). Contamination, especially by heavy metals, and other impurities arising from the synthesis of permitted dyes are stricdy controlled. Despite this effort, the number of usable organic dyes and of pigments derived from them has been drastically curtailed by regulatory action. 

Inorg nic Colora.nts. In addition to various white pigments, other inorganic colorants such as those Hsted in Table 9 are used in a number of cosmetic products. These usually exhibit excellent lightfastness and are completely insoluble in solvents and water. 

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